ELECTRIC MOTOR ROTOR

ROTOR POUR MOTEUR ELECTRIQUE

English Abstract

ABSTRACT.
A rotor for a small electric motor, useful for example
in a vehicle window raising device, has an armature
carried by a shaft and having slots in which electrical
conductors are wound and connected to a current
collector. The shaft has grooves at both sides of the
armature to a depth such as to permit the path of the
electrical conductors passing between non-consecutive
generally opposed slots during winding of the
conductors at the bottoms of the armature slots to be
substantially rectilinear.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a rotor for a small electric motor, including a
rotor shaft and an armature comprised of a stack of metal sheets
mounted on the rotor shaft to rotate therewith and having slots
in which electrical conductors are wound, the improvement
comprising: grooves in the rotor shaft at both ends of the
armature having a depth sufficient to allow the electrical
conductors passing across the ends of the armature adjacent the
shaft between non-adjacent substantially opposed slots to be
substantially rectilinear.
2. A rotor as claimed in claim 1, wherein said
grooves comprise: reduced diameter circumferential grooves in
the shaft, and at least some of said electrical conductors are
substantially tangent to the peripheral surfaces of said
grooves.
3. A rotor as claimed in claim 1, wherein the rotor
shaft further comprises a worm gear integrally formed on a
portion thereof axially spaced from one of said grooves, and a
current collector is mounted on said shaft operatively connected
to ends of the electrical conductors.
4. A rotor as claimed in claim 2, wherein the rotor
shaft further comprises a worm gear integrally formed on a
portion thereof axially spaced from one of said grooves, and a
current collector is mounted on said shaft operatively connected
to ends of the electrical conductors.

Description

3~;~0
The present invention relates to a rotor for a small
electric motor, in particular for a back-geared motor for auto-
motive use, such as a window raising device of the type compri-
sing, on a shaft, an armature, a current collec-tor and an end-
less screw produced integrally wi-th the shaft.
For such rotors it is necessary to use shafts having a
sufficient diameter to be able to produce the endless screw in
one piece and to provide the shaft with a good degree of
linearity whilst the back-geared motor is operating. When
winding the armature, the path of the turns of the armature
winding at the ~ottom oF the armature slots, when passing from
one slot to another, follows the outside of the shaft, of which
the diameter is greater than the virtual line connecting the
base of two slots receiving the same turn of the winding, as a
result of which the spatial requirement of the winding on both
sides of the armature increases more rapidly than the slots are
filled, this filling then being limited, as is the efficiency of
the back-geared motor for a given amount of space.
According to the present invention there is provided
in a rotor for a small electric motor, including a rotor shaft
and an armature comprised of a stack of metal sheets mounted on
the rotor shaft to rotate therewith and having slots in which
electrical conductors are wound, the improvement comprising:
grooves in the rotor shaft at both ends of the armature having a
depth sufficient to allow the electrical conductors passing
across the ends of the armature adjacent the shaft between
non-adjacent substantially opposed slots to be substantially
rectilinear.
Thus, the present invention overcomes the aforesaid
disadvantages and provides a rotor for a small electric motor,
in particular for a back-geared motor for automotive use, such
as a window raising device, of the type comprising, on a shaft,
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an armature composed of a stack of metal sheets with slots in
which electrical conductors are wound, a current collector and,
produced integrally with the shaft, an endless screw the shaft
being provided with grooves at both s-ides of the armature to a
depth such as to permit
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930
the path of the electrical conductors passing between
non-consecutive generally opposed slots, during winding
of the turns at the bottoms of the armature slots, to
be substantially rectilinear.
The following description with reference to the
attached drawin~s will show more clearly how the
invention may be produced.
Figure 1 is a longitudinal section of a rotor according
to the invention,
Figure 2 shows a rotor according to the invention
according to the section II II of Figure 1.
The rotor is formed in known manner by a shaft 1 which
has an armature 2 formed by a s.ack of metal sheets 7
with slots 8 and 9 in which windings are produced whose
ends are connected to a collector 3 supported by the
shaft 1, the rotor also including an endless screw
produced in one piece.
As the windings have been produced by the passage of
the conductor wire from a slot 8 to a slot 9, as shown
in Figure 2 in broken lines, the path of the winding
turns at the bases of the slots during the said
passage, form a curve 11 tangential to the outside of
the shaft 1, the diameter of the latter being chosen so
that it is sufficiently large not only to allow the
endless screw 4 to be produced in one piece, but also
to provide the shaft 1 with a good bending strength,
with the result that the spatial requirement of the
windings on both sides of the stack of metal sheets 7
quickly becomes considerable and does not allow the
slots 8 and 9 to be filled correctly.

In the rotor of the invention, grooves 5 are provided
in the shaft 1 on both sides of the stack 7, the depth
of these grooves 5 being defined such that the path 10
of the windings at the bases of the slots, e.g. from
the slot 8 to the slot 9, is rectilinear, which makes
it possible to obtain an additional amount of space
corresponding to the difference between the respective
diameters of the shaft and the groove, and consequently
to increase the number of turns in the said slots
without increasing the spatial requirement for passing
from one slot to another. The entire armature is then
impregnated by an insulator 6 of the epoxy resin type.
Such a rotor therefore makes it possible to produce a
more effective motor without changing its spatial
requirement.